The present invention generally relates to a method of and apparatus for manipulating two webs moving at different speeds and more particularly, to a method of and apparatus for separating discrete elements from a first substrate web moving at a first speed, after the first substrate web has been pre-perforated, and placing the discrete element separated from the first substrate web onto a second substrate web moving at a second speed.
Conventionally, absorbent articles for personal care usages, such as infant diapers, child training pants, adult incontinence garments, feminine sanitary napkins, and similar products for storing fluid bodily exudates, have been manufactured on an assembly line. The assembly line manufacture of these absorbent articles has involved manipulating first and second substrate webs moving at first and second different speeds, respectively. A number of machines and processes are known in the prior art for cutting discrete components from a first substrate web, traveling at a slower speed, and transferring the cut discrete components to a second substrate web, traveling at a faster speed. Many of these known machines and processes provide for the cutting of the discrete components at a point separated from the mechanism for transferring the cut component to the second web. In this situation, it often becomes difficult to maintain proper positioning and orientation of the cut component between the cutting operation and the placement of the cut component on the second substrate web. This problem is exacerbated in those cases where placement and orientation of the cut component on the second web are critical.
A solution to this problem has been proposed in the prior art which involves the cutting of the discrete components from the first substrate web after the first substrate web has been placed on a transfer roller. Indeed, the use of a cutting and transfer mechanism, such as an oscillating cam adjusted roller or OSCAR module, is taught in U.S. Pat. No. 5,716,478 (hereinafter xe2x80x9cthe ""478 patentxe2x80x9d), issued to Boothe et al. on Feb. 10, 1998, and entitled Apparatus And Method For Applying Discrete Parts Onto A Moving Web. The ""478 patent discloses how discrete elements or component parts of an absorbent article being manufactured, such as absorbent cores or inserts, leg elastics, waist elastics, tapes, and other fasteners including hook and loop materials or snaps, on a first continuously moving substrate web, may be cut from the first substrate web and applied to a second continuously moving substrate web of interconnected articles which is moving at a different speed on an assembly line.
The ""478 patent also discloses that the cutting of the discrete elements or component parts from the first substrate web is most preferably accomplished by use of a knife roll. The knife roll includes a plurality of cutting edges rotating about a shaft. The cutting edges of the knife roll cut the first substrate web into discrete elements or component parts at the junction between adjacent transfer segments of a transfer mechanism or OSCAR module.
However, the apparatus and method of the ""478 patent have certain drawbacks or problems associated therewith, because the cutting of the first substrate web into discrete elements or component parts involves competing concerns. On one hand, it is advantageous that the discrete elements or component parts are not cut from the web too early in the process in order to maintain the integrity of the web and thus, allow for easier transportation of the web from place to place. On the other hand, not cutting the discrete elements from the first substrate web early enough creates complications with adhesive application, if necessary, and also the location of the cutting equipment becomes difficult due to the confined space within which it must be positioned.
The ""478 patent teaches that the cutting of the first substrate web into discrete elements occurs at the junction between two adjacent transfer segments of the OSCAR module. This creates problems because cutting is typically done against a surface, such as an anvil, but as there is no anvil to cut against on the OSCAR module, if the rotation of the knife roll gets out of phase with the separation of the transfer segments, the knife roll may nick or damage the outer arched surface of the transfer segment. Thus, the useful life of the transfer segments may be shortened causing great expense for labor and parts in replacement and also down time of the assembly line.
It would be desirable if a method of and apparatus for separating a discrete element from a first substrate web moving at a first speed on an assembly line could be provided, without the need for a cutting device at a cutting station to cut the discrete element from the first substrate web, prior to placement of the discrete element on a second substrate web moving at a second speed.
In response to the discussed difficulties and problems encountered with respect to the prior art devices and methods, the present invention provides a method of and an apparatus for separating a discrete element from a first substrate web and placing the discrete element on a second substrate web moving at a different speed than the first substrate web.
In one aspect of the present invention, an apparatus for separating a discrete element from a first substrate web moving at a first speed and applying the discrete element onto a second substrate web moving at a second speed is provided. The apparatus includes a first station for making perforations across a width, at least partially through a thickness, and at predetermined spaced apart intervals along the first substrate web. The apparatus also includes a second station for separating the discrete element from the first substrate web at a first line of the perforations and then, placing the discrete element on the second substrate web.
In another aspect of the present invention, a method of separating a discrete element from a first substrate web moving at a first speed and applying the discrete element onto a second substrate web moving at a second speed is provided. The method includes the steps of: making perforations across a width, at least partially through a thickness, and at predetermined spaced apart intervals along a length of the first substrate web; separating the discrete element from the first substrate web along a first line of the perforations; and placing the discrete element on the second substrate web.